Induction linear electric motor

ABSTRACT

An induction linear electric motor comprising a pair of linear stators with their respective windings, movably mounted at the opposite sides of a stationary rotor member. Control of the travelling speed of the linear stators relative to the rotor in the direction of the motion of the traveling magnetic field, produced by the stators and their windings, is effected by displacing the stators and their windings relative to the rotor in a direction perpendicular to the direction of the motion of the magnetic field. When the travelling speed is controlled in the above-described member, with the stators displaced relative to the rotor, a portion of the magnetic flux produced by the stators is taken up by an auxiliary magnetic core of the disclosed; linear electric motor, this auxiliary magnetic core being disposed intermediate of the linear stators.

prising a gs, movably ry rotor member.

gs, is efgs relative to ry magnetic linear electric motor, thisauxiliary mag- Reierenoes Cited UNITED STATES PATENTS L m m s C n RJ 6664 99 IN 002 4/1932 Stewart l0/l958 Williams et al.

produced by the stators and their windin f linear stators with theirrespective windin ABSTRACT: An induction linear electric motor cornControl of the travelling speed of the linear stators relative to therotor in the direction of the motion of the travelin netic field fectedby displacing the stators and their windin the rotor in a directionperpendicular to the direction of the motion of the magnetic field. Whenthe travelling speed is controlled in the above-described member, withthe stators displaced relative to the rotor, a portion of the magneticflux produced by the stators is taken up by an auxilia core of thedisclosed;

netic core being disposed intermediate of the linear stators.

mounted at the opposite sides of a stationa pair 0 ulitsaMalo-Podvalnaya, l4 Kv. l3; Konstantin Alexeevich Bykov, ulitsaStreletskaya, l4, Kv. l2; Alexandr lvanovich Vishnikin, ulitsa Dovnar-Zapclskogo, 4, Kv. 39; Vladimir Andreevich Mishakin, ulitsaSelskokhozyabtrvennayn, 7/9/Kv. l9; Sergei Alexeevicl Rebrov, ulitsaNikolsko- Botanichakaya, l4 Kv. Itskbok Ammovich Spektor, ulilsaMuromskaya 3, RV. l5; Alexandr Grigorievich Shapovalenko, ulitaZatonskogo, Kv. 25, all of Kiev, U.S.S.R. Appl. No. 48,105

June 22, 1970 Patented Aug. 31, 1971 [72] Inventors Georgy IgnltievichIzhelya [22] Filed [54] INDUCTION LINEAR ELECTRIC MOTOR [51] Int. CLField of PATENIEU was! 19?:

sum 1 [IF 2 PATENIED MISS] IQ'II SHEET 2 OF 2 mnucrrou LINEAR ELECTRICMOTOR The present invention relates to electrical machines, and, moreparticularly, it relates to induction linear electric motors, and it canbe incorporated in traction means for an electrically propelled monorailvehicles, as well as in the driving means of the carriages of knittingmachines, of gantry cranes,

of the work tables of surface grinding machines, and in many othervehiclesand work performing machines.

Incorporation of induction linear electric motors'in the traction meansof monorail vehicles is known, where an induction electric motor propelsa monorail vehicle and comprises a pair of linear stators with theirrespective multiphase wound windings and a traction rotor-rail. Thetraction rail includes a massive bar of a ferromagnetic material, eg arolled steel shape without any additional machining. The traction railis rigidly secured to a beam support of the monorail way.

The windings of the linear stators are connected to a source ofmultiphase electric current and create a travelling or "running magneticfield, which moves longitudinally of the traction rail (which in thisknown linear electric motor acts similarly to the rotor of a commonlyknown induction electric motor, where the rotor is mounted for rotarymotion). The in- 'teraction of the running" magnetic field with eddycurrents induced thereby in'the massive traction rail creates .a forcedriving the stators for a linearrnotion longitudinally of the rail, Whenthe stators are connected, to a bogie of a monorail vehicle, this forceis utilized for propelling this monorail vehicle.

The connection of the linear-stators with the monorail vehicle shouldinclude elastic means, for the oscillations of the moving vehicle not tobe transmitted to the linear stators of the propelling electric motor.

'A desired value of the air gaps between the traction rail and theadjacent surfaces of the magnetic cores of the linear stators ismaintained by means of-a system of thrust and support rollers, arrangedto serve the purpose.

With the ferromagnetic rotor-rail .being positioned intermediate ot themagnetic cores of the linear stators, there appears therebetween a forceof magnetic attraction. In order to compensate for this force ofmagneticattraction, the linear stators are mounted by means ofspring-incorporating compensation devices.

However, the known apparatus of the above-described kind are not freefrom the following disadvantages: their travelling speed is controlledeither by switching over the poles or the windings, or by varying thefrequency of the power supply of the stator windings.

When the travelling speed is controlled by switching over the poles ofthe windings of the linear stators, it is virtual impossible to effectinfinite, stepless speed control; moreover, in this case the structureof the windings becomes complicated and the operation of the motorbecomes more vulnerable. On the other hand, if the travellingspeed iscontrolled by varying the frequency of the power supply, this involvesthe .use of costly tran'sducing means.

The present invention has for its aim the creation of an inductionlinear electric motor, which should feature infinite speed controlwithin a wide range of speed values.

These and other objects are attained in an induction linear electricmotor comprising a pair of linear stator structures with theirrespective windings, the stator structures being sup- I ported by acommon housing and being disposed, respectively,

at the opposite sides of a rotormember, in which linear electric motorthe travelling speed of the'relative motion of said stator structuresand said rotor member in the direction of the vmotion of the runningmagnetic field created by the stator motion of the running magneticfield; this induction electric linear motor, in accordance with thepresent invention, further comprising an auxiliary magnetic corepositioned above said rotor member, intermediate of said pair of linearstator structures, said auxiliary magnetic core being adapted to take upa portion of the magnetic flux produced by said stator-structures, assaid stator structures and said rotor member are displaced relative toeach other in said direction perpendicular to said direction of saidmotion of said running magnetic field, for the purpose of speed control.

According to a preferred embodiment of the present invention, it isadvisable for the auxiliary magnetic core to have a multileaf structureand for its length to be at least equal to the length of each one of thetwo linear stator structures.

The present invention will be better understood from the followingdetailed description of a preferred embodiment thereof, with duereference being had to the accompanying drawings wherein:

FIG. 1 shows schematically an induction linear electric motor, embodyingthe present invention, constructed for an application, as propellingmeans for a monorail vehicle (crosssectional view);

FIG. 2 shows the same, as FIG. 1, side view.

Referring now in particular to theappended drawings, the inductionlinear electric motor comprises two linear stators 1 (FIG. 1) with theirrespective windings 2. The two stators l are disposed at the oppositesides of a rotor 3, i.e. a structure ofwhich the function is similar tothat of a rotor in a commonly known rotary electric motor. It should beunderstood that in the herein disclosed embodiment of a linear electricmotor the rotor 3 is intended by no means for rotation rela tive tothe"stators l, or vice versa. So, here the terms stator" and rotor" areused for convenience only, without any further implications, as to theiractual mode of motion. In the herein disclosed exemplary embodiment ofthepresent invention, the linear electric motor is intended for use aspropelling means, e.g. for a monorail vehicle, and the rotor 3 is atraction rail made of a ferromagnetic material in the 'form of a massivel are carried by the housing structure 4 with provisions for theirlateral and vertical adjustment relative to the rotor-rail 3. Verticaladjustment of the stators 1 in relation to the rotor-rail 3 is effectedby means of a lifting mechanism 6 which is either electrically ormechanically actuated (FIG. 2). The values of the two air gaps 8 betweenthe opposite sides of the rotor-rail 3 (FIG. 1) and the respective onesof the two stators I are adjusted with the help of laterally adjustablethrust rollers 9 (FIG. 2). Inorder to reduce and balance the forcescreated by magnetic attraction between the linear stators 1 and therotorrail 3, acting upon the rollers 9, the linear stators 1 areconnected to the housing structure 4 through a respective pair ofcompensating spring devices 10 (FIG. 1). The entire housing structure 4with the stators l is supported on the rotor-rail 3 by means of at leasta pair of support rollers 11 (FIG. 2).

The herein disclosed induction electric motor operates, as follows.

When the windings 2 (FIG. 1) of the linear stators] are connected to amultiphase alternating-current power supply mains, the currents flowingthrough the windings 2 create a "running" magnetic field which moves ata constant speed in a direction perpendicular to the plane of thedrawing (FIG. 1), i.e. longitudinally of the rotor-rail 3. The speed ofthis motion is defined by the value of the pole division of the linearstators l (i.e. by the winding pitch of the windings 2 of the stators 1)and by the frequency of the power supply. With a predeter' mined setpitch of the windings 2 and a given pennanent frequency of the powersupply to the stators l, the speed of the motion of the magnetic fieldis constant.

The running," or moving magnetic field induces eddy currents in themassive ferromagnetic rotor-rail 3. The interaction of these eddycurrents with the running" magnetic field creates a propelling forcedirected longitudinally of the rotorrail 3 (perpendicularly to the planeof the drawing, FIG. 1) and applied to the stators l. The magnitude ofthis propelling force created by the herein disclosed linear electricmotor is proportional to the total area of the side surface total areaof the side surface of the rotor-rail 3, which is in engaged inelectromagnetic interaction with the two linear stators 1.

Since. as it has been already mentioned, in the herein describedembodiment of the present invention it is the rotorrail 3 which issecured to a stationary support, the action of the propelling forcebrings about linear motion of the stators 1 relative to the rotor-rail3. The speed of the motion of the linear stators l and, consequently, ofthe housing structure 4 will lag behind the speed of the motion of therunning" magnetic field by the value of slip, which, in the course ofset motion, depends on the resistance encountered by the motion of thevehicle propelled by the herein disclosed linear electric motor. Anyconvenient mechanical connection can be used for imparting the motion ofthe linear stators l and their supporting housing structure 4 to thevehicle propelled thereby, e.g. to the bogies (not shown) of a monorailvehicle.

Alternatively, the present invention can be embodied in a system wherethe linear stators l are stationary, and it isthe rotor-rail 3 which isadapted to move relative to the stators and to transmit its motion to aworking member or any other apparatus. In other respects the creation ofthe propelling force and utilization thereof are similar to theabove-described case, when the rotor-rail 3 is a stationary one.

The incorporation of the massive rotor-rail 3 in the herein disclosedelectric motor is responsible for the mechanical characteristicsthereof, i.e. the dependence of the propelling force upon the amount ofslip (or else on the speed of the motion of the linear electric motor)being a relatively sharply declining curve, the maximal electromagneticpropelling force being developed by the herein disclosed motor with theproportion of slip approaching 1.0 (the starting moment). By the stators1 being displaced in a direction perpendicular'to the direction of themotion of the running" magnetic filed (i.e. either vertically upward orvertically downward in FIG. 1), the area of electromagnetic interactionof the linear stators l and the rotor-rail 3 is reduced, which makes themechanical characteristic curve of the herein disclosed motor even moresharply declined, i.e. with the same amount of slip the motor would nowdevelop a smaller propelling effort (in other words, with the sameresistance to the motion of the vehicle the amount of slip would begreater, i.e. the speed of the motion of the motor and the vehiclepropelled thereby would be smaller). in this manner displacement of thelinear stators l relatively to the rotor-rail 3 can be used for infiniteadjustment of the speed of the motion of the electric motor, and,consequently, of the travelling speed of a vehicle or a work-performingmember propelled by the motor.

This displacement (upward raising in FIG. 1) of the linear stators l inrespect of the rotor-rail 3, which amounts to speed control, is effectedby the stator-lifting mechanism 6 which is either mechanically orelectrically actuated. The incorporation of the electric drive 7 of thestator-lifting mechanism 6 provides for remote control of the travellingspeed of the herein disclosed linear electric motor.

The provision of the auxiliary magnetic core makes it possible to eflecttravelling speed control without affecting any substantially the powercharacteristics of the herein disclosed electric,motor. When the linearstators l are lifted relative to the rotor-rail 3, the magnetic cores ofthe stators l are brought adjacent to the auxiliary magnetic core 5, andthe magnetic flux of the stators 1 becomes partially completed throughthis iliary .ElEEElli s9rr=.i 9 -!i9s 9,tha5 h current of the stators 1is not increased throughout the speed control range (on the contrary,the current may even decrease, on account of the magnetic B5565 bilityof the material of the auxiliary magnetic core being greater than thatof the material of the rotor-rail 5 The vertical dimension of theauxiliary magnetic core 5 is chosen to correspond to a desired range ofspeed control of the electric motor, and, preferably, it is 40 percentto 60 percent vertical dimension of the rotor-rail 3. The length of theauxiliary magnetic core 5 in the longitudinal direction is somewhatgreater than the length of each one of the two linear stators l, for theauxiliary magnetic core 5 to project at both ends thereof in thelongitudinal direction beyond the adjacent ends of the stators 1, sincethe thrust rollers 9 (H6. 2) which are positioned at both ends of thestators are displaced upon the auxiliary magnetic core 5, as the linearstators 1 are raised in the course of speed adjustment.

For no additional propelling or traction effort to be developed in thecourse of a speed control operation, i.e., when the auxiliary magneticcore 5 becomes penetrated by the magnetic flux of the linear stators 1,the auxiliary magnetic core 5 either should be made of a multileafstructure, with each leaf formed from electrical engineering steel sheetmaterial (as it has been already explained), or else it should be moldedfrom compressed ferrite powder.

Since it is a ferromagnetic bar (a steel rolled shape), which is used asthe rotor-rail 3 in the herein disclosed embodiment of the presentinvention, there is displayed a force of magnetic attraction between themagnetic cores of the linear stator 1 and the rotor-rail 3. The force ofmagnetic attraction applies a laterally directed effort to the thrustrollers 9 (FIG. 2) and helps to maintain a desired preadjusted extent ofthe magnetic gaps 8 between the two stators l and the respective sidesof the rotor-rail 3 (FIG. 1). In order to reduce the portion of themagnetic attraction force, which is transmitted to the thrust rollers 9,there are provided (as it has been already mentioned) at least twocompensation devices 10 including precompressed springs. The compressionforce of these springs is taken up by the common housing structure 4 ofthe herein disclosed electric motor. The reduction of the lateral loadof the thrust rollers 9 brings about reduced wearing out of the rollersand brings down the internal forces of the electric motor, which resistits linear motion.

The herein disclosed linear electric motor provides for its travellingspeed being controllable within a wide range of values.

Speed control of the herein disclosed linear electric motor does notinvolve any additional devices, besides the abovedescribedstator-lifting mechanism 6, and it does not affect the powercharacteristics of the electric motor.

An induction linear electric motor, constructed in accordance with thepresent invention, also provides for remote speed control, and it can beincorporated not only as propelling means for a monorail vehicle, butalso for other types of vehicles and production machines, e.g. thosewith work-performing members actuated for linear motion.

What we claim is:

1. An induction linear electric motor, comprising: a rotor member; apair of linear stator structures disposed, respectively, at the oppositesides of said rotor member; a pair of winding means carried,respectively, by said pair of linear stator structures; a source ofelectric current, said winding means being connectable to said source ofelectric current to produce a traveling magnetic field; an auxiliarymagnetic core means positionable intermediate of said pair of linearelectric stator structures for taking up at least a portion of amagnetic flux created by said pair of linear stator structures, as saidlinear stator structures are displaced relative to said rotor member ina direction perpendicular to the direction of the motion of saidtraveling magnetic field; a housing means supleast equal to the lengthof each one of said pair of linear staporting said pair of linear statorstructures.

2. An induction linear electric motor, as set forth is claim 1, whereinsaid auxiliary magnetic core means is of a laminated structure.

3. An induction linear electric motor, as set forth in claim 1, whereinthe length of said auxiliary magnetic core means is at I01 structures.

1. An induction linear electric motor, comprising: a rotor member; apair of linear stator structures disposed, respectively, at the oppositesides of said rotor member; a pair of winding means carried,respectively, by said pair of linear stator structures; a source ofelectric current, said winding means being connectable to said source ofelectric current to produce a traveling magnetic field; an auxiliarymagnetic core means positionable intermediate of said pair of linearelectric stator structures for taking up at least a portion of amagnetic flux created by said pair of linear stator structures, as saidlinear stator structures are displaced relative to said rotor member ina direction perpendicular to the direction of the motion of saidtraveling magnetic field; a housing means supporting said pair of linearstator structures.
 2. An induction linear electric motor, as set forthis claim 1, wherein said auxiliary magnetic core means is of a laminatedstructure.
 3. An induction linear electric motor, as set forth in claim1, wherein the length of said auxiliary magnetic core means is at leastequal to the length of each one of said pair of linear statorstructures.